P0131 an P0151 DTC Codes

[johnm]

Hi guys, I have sort of a weird problem.

 

I have 99, SE, 4x4, a/t that gives intermittent DTC/SEL/Check Engine light with codes P0131 and P0151 (Bank 1 and 2, front O2 sensor voltage low). I say intermittent because it will come on and then go off by itself. The truck has 140000 miles, so I initially thought the O2 sensors were going bad, so I replaced them. Still getting the codes.

 

The freeze data (which I've looked at a few times) shows that the codes get thrown at high engine loads, 50-80% load, MAP>60 KPA. If I drive "gently" for a couple days, the light goes off again. I don't know why engine load would have an effect on the O2 sensors. An intake manifold leak maybe? I did have the intake manifold gasket replaced a couple months ago to fix a coolant leak, that's about the time this problem started.

 

I've checked the O2 TSB for the voltage between the intake manifold and the block...well within tolerance (typically I get 6 millivolts, the tolerance on the TSB is 20 mV). Still I cleaned the wiring harness grounding points on the manifold, just on general principle.

 

The engine sensor monitors on the scan tool all read "OK".

 

The service manual says the code indicates that the O2 sensors are not reaching the maximum voltage the PCM looks for. OR that the voltage is consistently below 200 mV. Given that the codes will "self clear", I expect it's the former, rather than the latter reason.

 

Any thoughts or suggestions would be appreciated. I'm pretty much out of ideas on what it could be, but thought I would ask before I took it to the mechanic.

[johnm]

Moderator, is it possible to move this over to "The Garage?" It probably should have been posted over there to begin with.

[johnm]

Further examination of the service manual for these codes indicate that it could be any of the following problems that can be diagnosed with a full diagnostic computer and procedures (to which I don't have access).

 

Faulty O2 sensor

Ground fault in O2 circuit

Ground fault in PCM (from about 15 different locations)

Heat circuit failure for O2 sensors

Air intake leak

Low fuel pressure

Bad injectors

 

Though I guess I can rule out both new sensors being bad, and I suspect it has to be something that effects both sensors equally since it throws both codes at the same time.

 

So I guess I'm off to the mechanic. <sigh> This is not what I needed right now, money wise.

[johnm]

Took the truck in this morning for a diagnostic. Which showed no system faults, at all. The mechanic reset the learning computer and cleared the codes, which immediately came back after a trip to town. I asked him if it was possible that both new O2 sensors were bad. He said it's possible, that it's happened before.

 

Well, at $60-80 bucks a pop for sensors, and no return after use, I'm not really happy about that. So I'm stuck with replacing the new O2 sensors.

 

How do I tell if they are any good before I install them?

[adamzan]

No return after use? You mean they won't exchange them? How old are they?

[johnm]

No return after use? You mean they won't exchange them? How old are they?

 

Yeah, returns only in original packaging with receipt of unused items. Warranty return are preauthorized, by the new parts, send back the "bad part" and wait for them to say it's bad, then 10 days to get a refund, and I pay for shipping both ways for all the parts. I can't tell if I have to pay the restocking fee or not. That's what I get from ordering the parts online.

 

How old are they? Well, they've been in the truck for a little over a week, but there's no telling when they were manufactured.

Edited August 21, 2011 by johnm

[Precise1]

Here is a quote from when I posted about a Code P0158 for my wife's 99.0 R50 from a resident Nissan/Infinity mechanic.

 

As for your other codes, there is a few TSB's....NTB99-004b

 

IF YOU CONFIRM

If an applicable vehicle shows the MIL 'ON' and one or more of the following DTCs are stored in ECM:

 

96-97 MY Pathfinder vehicle: DTC P0130, P0150, P0136, or P0156.

98-00 MY Pathfinder vehicle: DTC P0131, P0134, P0138, P0140, P0151, P0154, P0158, P0160.

99-01 MY Frontier (V-6 Engine Only) or 00-01 MY Xterra (V-6 Engine Only) vehicle: DTC P0131, P0134, P0138, P0140, P0151, P0154, P0158, P0160.

02-04 MY Frontier (V-6 Engine Only), 02-04 MY Xterra (V-6 Engine Only)

DTC P1143, P0134, P0138, P1163, P0154, P1146, P1166, P0158.

 

ACTION

Use the Service Procedure in this bulletin to diagnose and repair the incident (if it should occur).

 

Perform a voltage drop test to check for a poor "ground " condition.

If necessary install a sub-harness between the intake manifold and the cylinder head to provide a direct path to "ground".

 

Seems like it is worth a try, ground issues cause a few problems with these vehicles.

I find the odds of both new O2 sensors being bad as slim. I strongly suggest you check out other possible causes rather than hrow $/parts at it.

 

B

[johnm]

Already checked the TSB, that is not the problem.

[adamzan]

Yeah, returns only in original packaging with receipt of unused items. Warranty return are preauthorized, by the new parts, send back the "bad part" and wait for them to say it's bad, then 10 days to get a refund, and I pay for shipping both ways for all the parts. I can't tell if I have to pay the restocking fee or not. That's what I get from ordering the parts online.

 

How old are they? Well, they've been in the truck for a little over a week, but there's no telling when they were manufactured.

Where did you get them? I usually buy from rock auto online and the 2 times I had to warranty something I just sent the old one in and as soon as they got a tracking number a new one was on the way.

[johnm]

Well, before I laid out money for new sensors, I figured I'd retest all the grounds and circuits with a new multimeter. $20 is less than $200, right?

 

Voltage from the O2 sensors, .3 to .6 (within spec range). As an aside, at the connectors on the harness side, the purple wire (right bank) and the purple/white wire (left bank) are the ones that send the signal to the ECM. Put the DMM read probe along the wire into the connector and black probe to ground to read the voltage. (Easier than trying to get to the ECM pins).

 

TSB99-004b, intake to ground voltage was anywhere from .15 to .31, and bounced around quite a bit. So, my prior test was done wrong, or the old DMM was reading wrong. So I will comply with the TSB directions before I do anything else. Sometimes it pays to double-check. So I owe a thanks to Precise1, if he hadn't said something, I probably wouldn't have.

[johnm]

Great, I found the TSB text online, including pictures of the harness, routing, and part numbers. I can probably build the harness myself, but out of curiosity, does anyone know the size of the bolt that goes in the cylinder head? Threads/inch or mm and diameter?

[johnm]

OK, so what size bolt is between 7mm and 8mm? I picked up some M7x1 bolts today, the thread pitch is right but the diameter is wrong. Is there such a thing as a 7.5mm bolt?

 

Well, it doesn't matter, I have no idea where to get such an odd-ball thing anyway. Guess I'll have to get the official nissan bolt.

Edited August 23, 2011 by johnm

[johnm]

Just to add another mystery twist to the intermittent "you'll never understand why I'm lit" SES light on my dash. Earlier this week, I built the harness and when installing it (without the mystery size bolt) disconnected the battery. While I'm still waiting for the bolts to arrive from Dallas, the SES light is off and has stayed off. So apparently, leaving the battery disconnected for an hour changed something? Who knows. Maybe some retired engineer at Nissan in Japan?

 

I'm still planning on installing the TSB grounding harness when the bolts come in, but it sure would be nice to understand the system a little better.

[johnm]

Just so this is out there for future searches:

 

The nissan bolt that goes into the right cylinder head is special. It's an M7.5x1, but 5-6mm of the bolt end has the threads stripped off and the bolt comes with an aluminum compression washer. So just bite the bullet and order it from the dealer. They cost like $1.36 each.

[Precise1]

Well, before I laid out money for new sensors, I figured I'd retest all the grounds and circuits with a new multimeter. $20 is less than $200, right?

 

Voltage from the O2 sensors, .3 to .6 (within spec range). As an aside, at the connectors on the harness side, the purple wire (right bank) and the purple/white wire (left bank) are the ones that send the signal to the ECM. Put the DMM read probe along the wire into the connector and black probe to ground to read the voltage. (Easier than trying to get to the ECM pins).

 

TSB99-004b, intake to ground voltage was anywhere from .15 to .31, and bounced around quite a bit. So, my prior test was done wrong, or the old DMM was reading wrong. So I will comply with the TSB directions before I do anything else. Sometimes it pays to double-check. So I owe a thanks to Precise1, if he hadn't said something, I probably wouldn't have.

Absolutely!! As for the thanks, you are welcome, I'm glad it helped. Kind of the point here...

 

OK, so what size bolt is between 7mm and 8mm? I picked up some M7x1 bolts today, the thread pitch is right but the diameter is wrong. Is there such a thing as a 7.5mm bolt?

 

Well, it doesn't matter, I have no idea where to get such an odd-ball thing anyway. Guess I'll have to get the official nissan bolt.

None normally and even 7mm is odd. The sizes usually go from M6 to M8...

 

Just so this is out there for future searches:

 

The nissan bolt that goes into the right cylinder head is special. It's an M7.5x1, but 5-6mm of the bolt end has the threads stripped off and the bolt comes with an aluminum compression washer. So just bite the bullet and order it from the dealer. They cost like $1.36 each.

Ok, that's just plain absurd!!

Thanks for the update, it makes this a well detailed thread.

 

Disconnecting the battery may have cleared the ECU and allowed some voltage to disipate??

I'd definitely still put the harness on though...

 

B

[johnm]

Yep, I installed the harness yesterday.

 

Reading a little about the O2 feedback sensor, fuel trim, ECM, OBDII, loop...not necessarily just on Nissan, though. It appears that an O2 sensor that had a slow failure (over time v. acute failure) can make the fuel trim learning adjust to the out of limits O2 voltage readings, so that even when the new O2 sensors go in, the fuel trim will still be off and will still trip the ECM fault.

 

Though nothing I read indicated this, I wonder if disconnecting the battery for such a long time reset the ECM and the fuel trim at the same time, which "fixed" the fault. I'm also not sure this is the same thing as the TSB problem of poor grounding of the ECM.

 

All speculation on my part, of course. The bottom line for me is that the truck is running well, I have no SES light, and my gas mileage has improved a few 1/10ths. Getting 17 mpg combined city highway, and 21 mpg on a recent highway trip.